If you have a long term visa eg retirement/marriage and you don’t want your visa to be cancelled when you stamp out you need to purchase a re-entry permit this allows you to come back and your visa is still valid note this will not extend your visa you must return before your visa/extension ends and in time to renew it.
I have never been asked he would just show is flight itinerary if he were, sorry I think this a simple question by the OP was made complicated, I think he’s just coming on holiday and a simple question of are you on a return/round trip could have been asked with the answers of 30 day emption entry.
Ah ok, I thought they were getting rejected because the arrival date is after their TM30 was previously submitted, so when re-entering you must register a new TM30 with the new date is on the system